Is your avatar photo you? And the pony on which you jumped 2'3"?
It's a lovely photo, and a nice demonstration of good elementary technique.
I'm going to ask you a personal question - do you tend to be a perfectionist in parts of your life?
Because I keep looking at the photo, and reading your description and thinking "Hmmmmmm. Either that photo is of someone else, of her on absolutely her best day ever that she's never been able to reproduce, or she's obssessing a tad."
If you were a student of mine, I might nag you to have a more generous release or put colored tape in the pony's mane to give you a marker for where I want you hands to be. Other than that, I'd probably be doing a lot of what you tell me you're already doing - working on position, jumping low single fences from a trot, and starting gymnastics. I will also tell you that you'd be my star student if you looked like that photo after a year of lessons. Jumpin 2'3" after a year of lessons is no small accomplishment, most of my students were still trotting crossrails and maybe a little gymnastic and had not graduated to a line or a course of crossrails at this point in time.
Alos, that pony is *really* jumping and rounding his back, not just stepping over, or pulling his landing gear up and out of the way.
So I think what you're describing is why we call it "learning to jump" rather than "just go ahead and jump."
I suspect your instructor already knows this about you, but you'd probably do well to learn some relaxation and breathing techniques to help with the anticipation (sorry, I read you post to mean you're tense because of anticipation and wanting to do well, rather than physical fear), or doing silly things like singing or reciting nursery rhymes as a distraction. The other thing that helps with anticipation tension is simple repetition - you just need to take more lessons and do it more often til it seems less like a big deal.
If you have any other photos, I'd be happy to critique, or if you want any other specific help, I'd be happy to help with that as well.